SUNRPC: fix races on PipeFS UMOUNT notifications
CPU#0 CPU#1
----------------------------- -----------------------------
rpc_kill_sb
sn->pipefs_sb = NULL rpc_release_client
(UMOUNT_EVENT) rpc_free_auth
rpc_pipefs_event
rpc_get_client_for_event
!atomic_inc_not_zero(cl_count)
<skip the client>
atomic_inc(cl_count)
rpc_free_client
rpc_clnt_remove_pipedir
<skip client dir removing>
To fix this, this patch does the following:
1) Calls RPC_PIPEFS_UMOUNT notification with sn->pipefs_sb_lock being held.
2) Removes SUNRPC client from the list AFTER pipes destroying.
3) Doesn't hold RPC client on notification: if client in the list, then it
can't be destroyed while sn->pipefs_sb_lock in hold by notification caller.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index b827a4b..41f180c 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -236,8 +236,6 @@
continue;
if (rpc_clnt_skip_event(clnt, event))
continue;
- if (atomic_inc_not_zero(&clnt->cl_count) == 0)
- continue;
spin_unlock(&sn->rpc_client_lock);
return clnt;
}
@@ -254,7 +252,6 @@
while ((clnt = rpc_get_client_for_event(sb->s_fs_info, event))) {
error = __rpc_pipefs_event(clnt, event, sb);
- rpc_release_client(clnt);
if (error)
break;
}
@@ -641,8 +638,8 @@
rcu_dereference(clnt->cl_xprt)->servername);
if (clnt->cl_parent != clnt)
rpc_release_client(clnt->cl_parent);
- rpc_unregister_client(clnt);
rpc_clnt_remove_pipedir(clnt);
+ rpc_unregister_client(clnt);
rpc_free_iostats(clnt->cl_metrics);
kfree(clnt->cl_principal);
clnt->cl_metrics = NULL;